The present invention relates to inverting operational amplifiers utilizing short-circuit transfer impedance in the feedback loop thereof for setting the gain of the amplifiers and, more particularly, to a differential to single ended operational amplifier utilizing a resistive tee network in the feedback loop that is referenced to the input for setting the gain of the amplifier.
There are a myriad of applications for high gain differential-to-single ended amplifier circuits. For instance, such an amplifier circuit is needed for use with standard pressure sensors that are required for very low pressure applications. Typical silicon piezoresistive pressure sensors commercially available may not be able to provide useable output voltages at very low applied pressures. An example is the MPX 2010 pressure sensor manufactured by Motorla, Inc. Although this pressure sensor works quite well it only has a sensitivity of approximately 2.5 mV/kPa. Hence, for very low pressures the differential output of the sensor must be grealty amplified.
One method to provide a large gain factor is the use of operational amplifiers having a feedback loop for controlling the gain of the amplifier. If the amplifier is to be utilized in combination with monolithic circuit applications it is desirable that resistive feedback elements be used that can be trimmed in commercial manufacture of these amplifiers. The use of a resistive tee network referenced to ground in the feedback loop of a single ended input and output amplifier is known. However, this known amplifier circuit is not suited for use for differential inputs.
Hence, a need exists for providing a high gain differential-to-single ended amplifier circuit having a resistive network in the feedback loop of the amplifier that is referenced to the applied input while providing a known output offset with zero input thereto.